Chapter 9: From Genes to Traits Flashcards

A set of vocabulary flashcards covering the regulatory networks, gene duplication, horizontal gene transfer, development of traits, and evolutionary constraints discussed in Chapter 9.

Complex Adaptations

Adaptations made of multiple components, encoded and controlled by many genes, that often require multiple mutations to achieve a fitness advantage.

Novel Traits

Traits that arise from mutations within a lineage and do not have obvious counterparts (homologs) in related lineages.

Regulatory Network

A system organized into a hierarchy where environmental signals trigger the expression of transcription factor genes, leading to a cascade of gene expression.

Transcription Factor

Activators that bind to the enhancer region of a control region to activate the transcription of genes.

Hox Genes

A family of genes that encode transcription factors to determine the identity and position of body parts during development.

Horizontal Gene Transfer

The acquisition of new genes from the environment or other organisms without sexual breeding, occurring within the same generation; more common in prokaryotes.

Gene Duplication

One of the most common sources of new genes, often caused by unequal crossing-over when homologous chromosomes align incorrectly.

Paralogs

Homologous genes that arise as a result of gene duplication within the same species.

Gene Family

A set of related paralogs that possess similar sequences and functions.

Gene Recruitment

The evolutionary transition where a gene or entire network is added to a different network of genetic interactions to foster a new adaptation.

Promiscuous Proteins

Proteins capable of performing two different functions, such as binding strongly to one molecule while weakly to a second target.

Pentachlorophenol (PCP)

A chlorine-based pesticide introduced in 1936 to kill wood-rotting fungi, which the bacterium $Sphingobium$ evolved to consume using recruited enzymes.

Crotamine

A muscle-destroying venom found in snakes that is closely related to defensin genes expressed in the pancreas.

Defensins

Genes originally evolved to fight infections, expressed in the pancreas of mammals and snakes, which were duplicated and recruited for venom production in snake ancestors.

Genetic Toolkit

The underlying gene network shared by almost all model organisms, such as mice and flies, used to control development.

Homologous Genes

Genes that are the same because they were inherited from a common ancestor, regardless of subsequent mutations.

MicroRNA (miRNA)

Small molecules that bind to specific sequences of mRNA to enhance or prevent translation, often keeping certain Hox genes shut down in specific regions.

Bmp4

A Hox gene expressed along the ventral side of mouse embryos that directs the development of the digestive system.

Dpp

A gene in flies that is homologous to $Bmp4$, which is expressed on the dorsal side to direct digestive system development.

Ortholog

A homologous gene in different species that is separated by a speciation event.

Sonic hedgehog (Shh)

A gene associated with the elongation of the limb bud; its reduced expression is linked to limb loss in snakes and dolphins.

Opsins

Molecules on the surface of photoreceptors that capture light; they belong to the family of G-protein-coupled receptors (GPCRs).

Crystallins

Highly stable proteins in the eye lens used to direct incoming light, which evolved from recruited heat-shock proteins.

$$\text{alpha-crystallins}$$

Specific crystallins in vertebrate eyes that originally functioned as heat-shock proteins to maintain the shape of over-heated proteins.

Pleiotropy

An occurrence where a single gene has multiple effects on the phenotype of an organism.

Antagonistic Pleiotropy

A condition where a mutation has beneficial effects on one trait but harmful effects on another, such as Bt toxin resistance causing sensitivity to gossypol in pink bollworms.

Recurrent Laryngeal Nerve

A branch of the vagus nerve that wraps around a major blood vessel, illustrating an evolutionary imperfection inherited from fish ancestors.

Parallelism

Independent mutations in different lineages that result in approximately the same phenotype.

Deep Homology

The underlying similarities of genetic networks that arose very long ago in a deep evolutionary branch.